Bondable polyamide

ABSTRACT

Self-bondable polyamides are prepared by reacting an aromatic diisocyanate or diamine with a mixture of terephthalic acid and an aliphatic dibasic acid having at least 6 carbon atoms. These self-bondable amides can also be used as topcoats for wires having basecoats of another polymer, e.g. a polyester, polyester-imide, or polyamide-imide.

This is a division of application Ser. No. 514,035, filed July 15, 1983 which is a division of Ser. No. 311,385, filed Oct. 14, 1981, now U.S. Pat. No. 4,420,535.

BACKGROUND OF THE INVENTION

The present invention relates to a novel self bondable aromatic aliphatic polyamide.

An all-aromatic polyamide as made in accordance with Allard U.S. Pat. No. 3,642,715 does not exhibit self-bonding characteristics even when tested via the NEMA Bonding Test No. 57.1.1.2. at temperatures up to 260° C. The all-aliphatic polyamides as described by the work of Otis U.S. Pat. No. 4,216,263 and Kawaguchi U.S. Pat. No. 4,163,826 are thermoplastic in nature and exhibit good bonding characteristics but do not offer the excellent humidity resistance and resistance to attack by refrigerants as do the aromatic-aliphatic polyamides of the present invention.

Gilman U.S. Pat. No. 2,268,586 has a broad teaching of making polyamides by reacting a dibasic acid with a diisocyanate but does not show self-bondable polyamides.

Onder U.S. Pat. No. 4,072,665 discloses a novel copolymer of the formula ##STR1## where R is 60 to 85 percent of an aliphatic dibasic carboxylic acid with (CH₂)_(x) recurring units and x being an integer of 7 to 12 inclusive, the remaining 15 to 40 percent of R being m-phenylene. The proportion are indicated to be critical in Onder. Onder also indicates on column 6, lines 43-52 that a portion of the recurring units up to 10% can have R from a different dicarboxylic acid, e.g. terephthalic acid. Onder uses his products for many things including wire coatings, column 6, lines 11-22. However, Onder makes no mention of a solution cast film which is baked and yet retains self-sealing or adhesive properties.

SUMMARY OF THE INVENTION

There have now been prepared random aromatic-aliphatic copolyamides having the recurring unit ##STR2## where AL is the divalent hydrocarbon residue of an unsubstituted aliphatic dicarboxylic acid having 6 to 36 carbon atoms or more, usually AL is (CH₂)_(x) where x is 4 to 34, preferably 6 to 12, most preferably 10. Examples of such dicarboxylic acids include adipic acid, sebacic acid, azelaic acid and dodecanedioic acid. However, AL can be the residue of an unsaturated dicarboxylic acid, e.g. dimerized linoleic acid or dimerized oleic acid or dimerized tall oil. R is tolylene, phenyl, ##STR3## where F is O, CH₂ or SO₂. Less preferably all or a part of R can be cycloaliphatic, e.g. cyclohexylene or methylenedicyclohexyl, Ar is p-phenylene, y is 35 to 80% of the recurring units and z is 65 to 20% of the recurring units. Usually y is 40 to 70% of the recurring units and preferably y is about 60 to 70%, most preferably 65% of the recurring units. If y is above 70% there is a tendency to gel on standing.

The copolyamides can be prepared in conventional manner by reacting a mixture of the dicarboxylic acids, e.g. dodecanoic acid and terephthalic acid with a diisocyanate, e.g. toluene diisocyanate or methylene diphenyl diisocyanate, or with the corresponding diamine, e.g. toluene diamine, 4,4'-methylene diphenyl diamine (methylene dianiline), oxydianiline, phenylene diamine, diaminodiphenyl sulfone, or a mixture of such diisocyanates or of such diamines. As indicated there can also be employed a minor amount of 4,4'-methylene diphenyl diamine or cyclohexyl diamine. In reacting with the diamine rather than the diisocyanate it is of course possible to employ other acylating agents than the acid, e.g. there can be used the acyl halides, e.g. the dichloride or dibromide of dodecandioic acid or the lower alkyl esters, e.g. dimethyl dodecandioate, diethyl dodecandioate, and dibutyl dodecanedioate.

Preferably in the formula R has the mole percent ratio of 4-methyl-m-phenylene/2-methyl-m-phenylene/4,4'-methylene diphenylene in the range of 40/10/50 to 80/20/0. The reaction is carried out in an amide solvent such as N-methyl-2-pyrrolidone (NMP).

The copolyamides of the invention are useful as a self-bonding coating for magnet wire. This coating is usually applied in an amide based solvent system, e.g., N-methyl pyrrolidone or a mixture of N-methyl pyrrolidone and an aromatic hydrocarbon. The major advantages offered by this novel enamel are:

(1) High temperature retention of bond strength.

(2) The quality of the base coat is not lessened, and in some cases, the quality of the base coat is improved by the bonding overcoat.

(3) The coating is resistant to attack by refrigerants.

(4) The coating has improved humidity resistance.

(5) The coating has improved chemical resistance.

(6) The coating is less costly than commercially available alternatives.

(7) The end user's cost is reduced by elimination of a costly secondary insulation.

(8) By eliminating the solvent-borne secondary insulation requirement, the bond coat offers obvious ecological advantages.

(9) Good adhesion to self-supporting high-temperature films.

Thus, the novel, self-bonding wire coating provides the magnet wire user an economical and ecological alternative with significant improvements in bond strengths, hermetic resistance, and chemical resistance when compared to other self-bond wire coatings. This novel coating also offers the motor manufacturer an option to eliminate secondary insulations as the self-bonding wire coating will produce results equivalent to or better than those achieved with the secondary insulations currently used.

It was previously pointed out that the copolyamides of the present invention are superior, in humidity resistance and resistance to attack by refrigerants, to the products of Otis U.S. Pat. No. 4,216,263. Thus when a sample of a polyamide as described in Otis is subjected to a 100 percent humidity at 70° C., it exhibits an initial resistance of about 370,000 megohms. After aging one week, the megohm resistance was about 280,000 megohms; after two weeks, the resistance had dropped to about 160,000 megohms. The aromatic-aliphatic polyamide of the present invention (based on Mondur TD-80, 4,4-methylene diphenylene-diisocyanate, terephthalic acid and dodecane-dioic acid), when submitted to this test, gave the following results:

    ______________________________________                                                      After        After                                                Initial      One Week     Two Weeks                                            ______________________________________                                         422,000 megohms                                                                             900,000 megohms                                                                             820,000 megohms                                      ______________________________________                                    

The dielectrics of the all-aliphatic polyamides of Otis were reduced by 50 percent after two weeks at 100 percent relative humidity and 70° C. The aromatic-aliphatic polyamides of this invention, however, did not significantly change after the two-week aging. The all-aliphatic nylons are true thermoplastics, unlike the aromatic-aliphatic polyamides of the invention which, when initially bonded at 200° C., retain good bond strength at 200° C. The aromatic-aliphatic polyamides of the invention, when coated over a polyester of the type described by Meyer in U.S. Pat. Nos. 3,201,276 and 3,211,585, will upgrade the base polyester to a NEMA Class 155° C. or greater magnet wire coating system. The entire disclosure of the Meyer patents are hereby incorporated by reference and relied upon. When coated over other wire enamels or wire enamel systems, the inherent properties of the coated wire are not adversely effected. The aliphatic-aromatic polyamides of this invention will self-bond at temperatures of 170° C. or greater when tested in accordance with NEMA Test Specification 57.1.1.2 with resulting bond strengths of greater than seven pounds when broken at 180° C.

When this novel enamel is coated over a self-supporting, high-temperature film, such as a polyimide, polyparabanic acid, polyamide, or polyamide-imide film, then baked to dry, the film may then be self-bonded and will exhibit outstanding inner laminar adhesion.

If a polyamide, in 70/30 NMP/xylene, is made from 100% of an alkanedioic acid such as dodecanedioic acid and a mixture of toluene diisocyanate and methylene diphenyl diisocyanate, then the enamel product gels on standing. In fact there is a tendency for gelation to occur if the amount of dodecanedioic acid goes above 70 mole percent and especially above 78 mole percent based on the total of dodecanedioic acid and terephthalic acid.

Among the advantages of the copolyamides of the invention, in addition to or in amplification of those set forth above are:

(1) The wire coating is bondable at 200° C. and yet retains good bond strength at 180° C. However, once the polymer is "Heat Set" above the apparent glass transition temperature of the aromatic-aliphatic polyamide, the apparent glass transition temperature increases, thus giving some thermoset properties to the coating.

(2) The aromatic-aliphatic polyamide system of the invention is the only amide bonding system offered which is not in part a physical blend of an all aliphatic amide such as Nylon 6;6,6; 11 or 12. The aromatic-aliphatic polyamide is, however, an in situ reaction product of an aromatic diacid and an aliphatic diacid, preferably with a blend of aromatic diisocyanates to yield a random aromatic-aliphatic polymer. The preferred reactants are terephthalic acid and dodecanedioic acid with toluene diisocyanate and methylenediphenyl diisocyanate in a 70:30 mole ratio. The reaction is carried out in an amide-type solvent such as N-methyl-2-pyrrolidone.

(3) The aromatic-aliphatic polyamide, when coated over ISONEL 200, yields a Class 155° C. magnet wire; and, with the exception of the heat shock, displays Class 180° C. properties.

When coated over ISOMID, excellent properties as a Class 180° C. magnet wire are observed.

(4) The aromatic-aliphatic polyamide coated over ISONEL 200 pases the A. O. Smith Freon Blister Test; conventional Nylon 6,6 coated over ISONEL 200 fails this test.

(5) The moisture resistance of the aromatic-aliphatic polyamide is also superior to the Nylon 11 types.

(6) The aromatic-aliphatic polyamides offer a significant cost advantage over the systems based upon Nylon 11 or 12.

As indicated above the enamels of the invention exhibit good bond strengths when coated over ISONEL 200 and ISOMID wire enamel. Thus when bonded at 200° C. for 20 minutes they have shown bond strengths of 1 to 6.2 lbs. and even up to 7.4 pounds at 180° C. without degrading other wire properties by application of the bond coat.

The heat-bondable copolyamide film of the invention can be applied by conventional wire coating techniques to give a wire that may be wound into coils, armatures, stators, etc., and heat bonded, thereby eliminating the need for an impregnating varnish, to give a wire-insulation system of unusual thermal resistance. In the process of eliminating the need for a varnish dip, the need for expensive dipping apparatus ovens, lengthy cure cycles, and high energy costs are eliminated.

The bondable copolyamide of the invention can be employed, for example, as a top coat over a wire having a base coat or coats of, for example:

1. a glycerine or other aliphatic polyhydric alcohol polyester, e.g. glycerine-ethylene glycol terephthalate polymer as in Precopio U.S. Pat. No. 2,936,296,

2. tris(2-hydroxyethyl)isocyanurate polyester, e.g. tris(2-hydroxyethyl)isocyanurateurethylene glycol-terephthalate polymer as in Meyer U.S. Pat. No. 3,342,780,

3. a polyester coated with an amide-imide polymer, e.g. the polyester of Precopio or Meyer U.S. Pat. No. 3,342,780 coated with an amide-imide polymer as shown in Koerner U.S. Pat. No. 3,022,200 and Standard Oil British Pat. No. 1,056,564.

4. a polyester-imide which is the reaction product of THEIC, ethylene glycol, terephthalic acid (or isophthalic acid), methylene dianiline (or oxydianiline) and trimellitic anhydride, e.g. as in Meyer U.S. Pat. No. 3,426,098. In place of THEIC, there can be used glycerine, e.g. as in the polyester-imides of Schmidt U.S. Pat. No. 3,697,471. Likewise, there can be used as the base coat the diethylene glycol or triethylene glycol monoether modified polyesterimide resins of Keating U.S. Pat. No. 4,119,608,

5. amide-imide coated polyester-imide as in the Keorner and Standard Oil patents,

6. monolithic amide-imide as in the Standard Oil patent,

7. polyimide such as Pyre ML as in Edwards U.S. Pat. Nos. 3,179,634; 3,179,630; 3,179,631; 3,179,632, and 3,179,633,

8. as a coating over an acrylic (acrylic-methacrylic acid ester) top coated polyimide of the type of Lecton (DuPont),

9. conventional Formvar (polyvinyl formal), epoxy (e.g. bisphenol A-epichlorohydrin), urethane, and nylon top coated urethane. The entire disclosures of the Meyer U.S. Pat. No. 3,342,780, Precopio, Koerner, Standard Oil, Keating, Meyer U.S. Pat. No. 3,426,098, and the Edwards patents are hereby incorporated by reference and relied upon.

The wire enamels can be applied to either bare or base coated copper, aluminum, silver, or other wires using conventional coating procedures and wire speeds, e.g., 30-150 ft/min. and curing the wire is carried out at conventional temperatures. The speed is adjusted according to wire size and enamel to obtain optimum cure as is known in the art.

The copolyamides of the invention are also useful as bondable coatings over film wrapped wire, e.g.

1. Kapton--a polyimide film of DuPont as in the Edwards patents.

2. Nomex--a DuPont aromatic polyamide (isophthalic acid with an aromatic diamine).

The copolyamides of the invention can be used as adhesives to apply over self-supporting films, e.g. used in printed circuit boards and capacitors. Typical self-supported films include Kapton polyimide, Mylar (polyethylene terephthalate) polyester, Nomex, polytetrafluoroethylene and perfluoroethylene-perfluoropropylene copolymer.

The copolyamides of the invention can be employed as cast films for adhesive use. The film is cast from solution and can then be used as an adhesive.

In film, strand or filament form the copolyamide can be used as a substitute for Dacron in wrapped glass cloth. Dacron is not high temperature resistant. Hence replacing the Dacron filaments by filaments of the copolyamide of the invention gives higher temperature resistant products.

Nomex is available as cast or sheet insulation. The heat bondable copolyamide of the invention can be used as a wrapping therefore to hold the Nomex together.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of bond strength vs. percent of aliphatic dibasic acid (dodecanedioic acid); and

FIG. 2 is a graph comparing the bond strength of the copolyamide with that of Nylon 11.

The composition can comprise, consist essentially of, or consist of the materials set forth.

EXAMPLE 1

This example is a working example of the present invention.

    ______________________________________                                                                  Load                                                  Raw Materials            in Grams                                              ______________________________________                                         (1) N--methyl-2-pyrrolidone                                                                             4168                                                  (2) Toluene diisocyanate (Mondur TD-80)*                                                                1033                                                  (3) 4,4' Methylene diphenyldiisocyanate                                                                  637                                                  (4) Terephthalic Acid     494                                                  (5) Dodecanedioic Acid   1267                                                  (6) Xylene               2243                                                  (7) N--methyl-2-pyrrolidone                                                                             1050                                                  ______________________________________                                          *Mondur TD80 is a 80/20 blend of 4methyl-m-phenylene diisocyanate and          2methyl-m-phenylene diisocyanate and is commercially available from Mobay      Chemical Company, Pittsburgh, Pennsylvania.                              

Parts one through three charged at room temperature into a 12-liter, round-bottom reaction flask, equipped with an agitator, a thermometer, an inert gas purge, and a water-cooled condenser fitted with a flexible tube which was immersed in a flask containing a mixture of water and denatured ethyl alcohol. (The reaction by-products carried through the condenser by the carbon dioxide and nitrogen are trapped in the water-alcohol solution). Parts four and five were added at room temperature with agitation and a blanket of nitrogen was applied over the reaction. The temperature was raised slowly by use of an electric heating mantel to approximately 75° C. when carbon dioxide evolution began. The external heat was then reduced and the temperature of the batch was allowed to rise over a four-hour time period to approximately 170° C. At about 80° C., the batch became clear. After an approximate four-hour hold at 170° to 175° C., the reaction was allowed to cool slowly to room temperature over night. The next morning the reaction mixture was sampled and a 60 percent solution in N-methyl-2-pyrrolidone was determined to have a viscosity at 25° C. on the Gardner-Holdt scale of W 1/2. Parts six and seven were then added. The final viscosity of the solution at 25° C. was Z on the Gardner-Holdt scale, or 2,500 centipoises as measured by a Brookfield RVT Viscometer.

The percent non-volatiles of the solution were determined to be 27 percent by baking a two-gram sample for two hours at 200° C. The specific gravity of the solution was determined to be 1.025 at 25° C. This solution was then used to overcoat a commercially available polyester (ISONEL 200)**. The test properties were as shown in Table One. It was also coated over a commercially available polyester-imide (ISOMID)*** and tested as shown in Table One.

The temperature of coating the wires in all of the examples was 370°-480° C.

EXAMPLE 2

    ______________________________________                                                                  Load                                                  Raw Materials            in Grams                                              ______________________________________                                         (1) N--methyl-2-pyrrolidone                                                                             4168                                                  (2) Toluene diisocyanate (Mondur TD-80)                                                                 1033                                                  (3) 4,4-Methylene diphenyldiisocyanate                                                                   637                                                  (4) Terephthalic Acid     494                                                  (5) Dodecanedioic Acid   1267                                                  (6) Xylene               1982                                                  (7) N--methyl-2-pyrrolidone                                                                              910                                                  ______________________________________                                    

The reaction was carried out much in the same fashion as described in Example One, with the exception of the over night cooling step. The reaction medium was sampled after a three-hour hold at 165° to 180° C. at 60 percent in N-methyl-2-pyrrolidone and found to have a viscosity of V 1/2 at 25° C. on the Gardner-Holdt Scale. The batch was then reduced with six and seven to a final viscosity of Y 1/4 at 25° C. on the Gardner-Holdt Scale at 28.45 percent non-volatiles determined as described in Example One.

The material was then coated over a polyester (ISONEL 200), a polyester imide (ISOMID), a polyester overcoated with a polyamide-imide, (ISONEL 200, overcoated with trimellitic anhydride-methylene dianiline polymer), a polyamide-imide (trimellitic anhydride-methylene dianiline polymer) wire coating and as a monolithic enamel. The results of the testing on the coated conductors are as shown in Table One.

EXAMPLES 3 THROUGH 8

Examples Three through Eight describe the effects of the mole percent ratio of aliphatic diacid to aromatic diacid. The effects on bond strength are shown on Graph Number One. (Bond strength versus percent aliphatic diacid). Also shown on Graph Number One is the relationship of bond strength to breaking temperature. The other properties of the coated conductors are as displayed in Table One.

The general procedure for making these enamels is as described in Example One.

    ______________________________________                                                    Example                                                                        3    4      5       6    7    8                                     Reactants    Batch Weight                                                      ______________________________________                                         (1) N--methyl-2-                                                                            644    611    623   633  655  664                                 pyrrolidone                                                                    (2) Toluene  159    159    159   159  159  159                                 diisocyanate                                                                   (3) 4,4'-methylene                                                                           98     98     98    98   98   98                                 diphenyl                                                                       diisocyanate                                                                   (4) Terephthalic                                                                             76    141    118    97   54   32                                 Acid                                                                           (5) Dodecanedioic                                                                           194    104    135   164  224  254                                 Acid                                                                           (6) Xylene   327    382    346   331  335  366                                 (7) N--methyl-2-                                                                            119    140    241   140  126  210                                 pyrrolidone                                                                    Gardner-Holdt                                                                               Y 3/4  X 1/2  Y+    Z+   Y 1/4                                                                               Y                                   Viscosity @ 25° C.                                                      Percent Non- 27.8   24.9   25.2  26.8 23.8 25.7                                Volatiles                                                                      Determined                                                                     2 gm., 2 hr.,                                                                  200° C.                                                                 ______________________________________                                    

EXAMPLE 9

This example describes the use of an aliphatic acid as described in the disclosure where X equals four.

    ______________________________________                                         Reactants              Batch Weight                                            ______________________________________                                         (1) N--methyl-2-pyrrolidone                                                                           600                                                     (2) Toluene diisocyanate                                                                              171                                                     (3) 4,4' Methylene diphenyldiisocyanate                                                               105                                                     (4) Terephthalic Acid   81                                                     (5) Adipic Acid        133                                                     (6) Xylene             257                                                     Gardner-Holdt Viscosity (25° C.)                                                               W 1/2                                                   Determined Percent Non-Volatiles                                                                      32.4                                                    (2 grams, 2 hours, 200° C.)                                             ______________________________________                                    

This example was prepared as described in Example One.

The properties of this enamel when used to overcoat ISOMID are as described in Table One.

EXAMPLE 10

This example demonstrates the use of a dibasic acid where X equals eight.

    ______________________________________                                         Reactants              Batch Weight                                            ______________________________________                                         (1) N--methyl-2-pyrrolidone                                                                           560                                                     (2) Toluene diisocyanate                                                                              145                                                     (3) 4,4' Methylene diphenyl diisocyanate                                                               89                                                     (4) Terephthalic Acid   69                                                     (5) Sebacic Acid       156                                                     (6) N--methyl-2-pyrrolidone                                                                           207                                                     (7) Xylene             411                                                     Gardner-Holdt Viscosity (@ 25° C.)                                                             X 1/2                                                   Determined percent Non-Volatiles                                                                      24.2                                                    (2 grams, 2 hours, 200° C.)                                             ______________________________________                                    

This example was prepared in accordance with the procedure described in Example One.

The test results obtained when this enamel was applied over 18-AWG copper wire coated with ISOMID are shown in Table One.

EXAMPLE 11

This example indicates that the allowable number of methylene groups between the two carboxyl groups of the aliphatic diacid may not have an upper limit.

    ______________________________________                                         Reactants              Batch Weight                                            ______________________________________                                         (1) N--methyl-2-pyrrolidone                                                                           585                                                     (2) Toluene diisocyanate                                                                               94                                                     (3) 4,4' methylene diphenyl diisocyanate                                                               68                                                     (4) Terephthalic Acid   45                                                     (5) Empol 1010*        283                                                     (6) N--methyl-2-pyrrolidone                                                                           140                                                     (7) Xylene             310                                                     Gardner-Holdt Viscosity (@ 25° C.)                                                             Y 1/4                                                   Determined percent Non-Volatiles                                                                      29.4                                                    (2 grams, 2 hours, 200° C.)                                             ______________________________________                                          *Empol 1010 is a C.sub.36 dimerized fatty acid available from Emery            Industries, Inc., Cincinnati, Ohio.                                      

This reaction was cooked in accordance with the procedure outlined in Example One.

The test results obtained when this enamel was applied over 18-AWG copper wire coated with ISOMID are shown in Table One.

EXAMPLE 12

This working example demonstrates the use of a cyclic aliphatic diisocyanate to replace a portion of the aromatic diisocyanate.

    ______________________________________                                         Reactants             Batch Weight                                             ______________________________________                                         (1) N--methyl-2-pyrrolidone                                                                          600                                                      (2) Toluene diisocyanate                                                                             146                                                      (3) Desmondur W*       97                                                      (4) Dodecanedioic Acid                                                                               179                                                      (5) Terephthalic Acid  76                                                      (6) N--methyl-2-pyrrolidone                                                                          155                                                      (7) Xylene            323                                                      Gardner-Holdt Viscosity (@ 25° C.)                                                            Z 1/4                                                    Determined Percent Non-Volatiles                                                                     27.5                                                     (2 grams, 2 hours, 200° C.)                                             ______________________________________                                          *Desmondur W is a cycloaliphatic diisocyanate available from Mobay             Chemical Company, Pittsburgh, Pennsylvania.                              

This enamel was prepared as described in Example One. It was then applied as an overcoat to ISOMID-coated copper wire. The test results obtained from this construction are as shown in Table One.

EXAMPLE 13

This example shows the use of all toluene diisocyanate to make an acceptable bond coat.

    ______________________________________                                         Reactants             Batch Weight                                             ______________________________________                                         (1) N--methyl-2-pyrrolidone                                                                          606                                                      (2) Toluene diisocyanate                                                                             226                                                      (3) Dodecanedioic Acid                                                                               194                                                      (4) Terephthalic Acid  76                                                      (5) N--methyl-2-pyrrolidone                                                                          210                                                      (6) Xylene            350                                                      Gardner-Holdt Viscosity (@ 25° C.)                                                            X 1/4                                                    Determined percent Non-Volatiles                                                                     27.2                                                     (2 grams, 2 hours, 200° C.)                                             ______________________________________                                    

This example was prepared using the procedure described in Example One. However, as indicated no 4,4'-methylene diphenyl diisocyanate was employed.

When coated over 18-AWG ISOMID coated wire, the bond coat gave the properties as shown in Table One.

COMPARATIVE EXAMPLE 1

A commercial solution of Nylon 66 was coated over a polyester wire enamel, namely, ISONEL 200. The resulting magnet wire exhibited the properties shown in Table One.

COMPARATIVE EXAMPLE 2

A solution of Nylon 11 was prepared in accordance with U.S. Pat. No. 4,216,263 by Otis. The viscosity of this solution was approximately Z51/2 on the Gardner-Holdt Scale at 25° C. The percent non-volatiles of the solution was determined to be 16.1 percent by baking a two-gram sample for two hours at 200° C. This enamel solution was coated over a polyester-imide of the ISOMID type on AWG-24 copper wire. The electrical and bonding test results are shown in Table One.

COMPARATIVE EXAMPLE 3

A solution of Nylon 11 was prepared in accordance with U.S. Pat. No. 4,216,263 by Otis. The viscosity of the solution was approximately Z23/4 on the Gardner-Holdt Scale at 25° C. at approximately 16.1 percent non-volatiles determined as in Example One. This enamel was coated over a polyesterimide wire coating, namely ISOMID on 18-AWG copper wire. The test results are shown in Table One. A comparison of the bond strength of this example to the preferred composition of this disclosure as described by Example One is shown on Graph Number Two.

COMPARATIVE EXAMPLE 4

A solution of Nylon 11 was prepared in accordance with U.S. Pat. No. 4,216,263 Otis. The viscosity of this solution was approximately Z31/2 on the Gardner-Holdt Scale at 25° C. The percent non-volatiles determined as in Example One were 16.8 percent. This enamel was coated over a polyester wire coating, namely ISONEL 200 on 18-AWG copper wire. The electrical and bonding test results are as shown in Table One.

    ______________________________________                                         Abbreviation Key for Table 1                                                   ______________________________________                                         F.O.M.      Figure of Merit                                                    Hrs.        Hours                                                              FPM         Feet per Minute                                                    VPM         Volts Per Mil                                                      Base Coat: PE                                                                              Polyester of the ISONEL ® 200 type                             PEI         Polyester-imide of the ISOMID ® type                           PAI         Aromatic polyamide imide                                           PAI/PE      Polyamide-imide based upon                                                     4,4' methylene diphenyl diisocyanate                                           and trimellitic anhydride                                                      coated over a polyester of the                                                 ISONEL ® type                                                  None        Indicates the bond coat was applied                                            in eight passes to obtain a three-                                             mil build                                                          Build       total increase in the wire diameter                                            as a result of the coating.                                        Wire Size   All AWG sizes                                                      Speed       The rate the wire traveled as it                                               was coated in multiple passes and baked                                        in a 15-foot, gas-fired oven.                                      Appearance: G                                                                              Indicates good or smooth surface.                                  VSW         Indicates smooth surface with a                                                very slight wave.                                                  SW          Indicates minor flaws in the coating                                           surface                                                            Heavy Grain Indicates a rough surface without                                              blisters                                                           Rough       Is an indication the coating is                                                unacceptable as it may contain                                                 blisters, or a very heavy grain,                                               or an extreme wave.                                                (+)         Indicates slightly better than given                                           rating                                                             (-)         Indicates slightly worse than given                                            rating                                                             Snap        Measured in accordance with NEMA                                               Standards Publication Part 3,                                                  paragraph 3.1.1.                                                   Mandrel After Snap                                                                         Smallest mandrel around which wire                                             which has been "snapped" as above can be                                       wound without exhibiting surface                                               cracks.                                                            Abrasion    Measured in accordance with NEMA                                   Unilateral  Standard Publication Part 3,                                       Scrape      paragraph 59.1.1.                                                  Windability 1500 volts are passed through a                                                six foot long wire sample which is                                             wrapped around a specified mandrel.                                            The mandrel moves along the wire                                               at fixed rate elongating and                                                   abrading the wire. Failure is                                                  described when three shorts occur                                              along the surface of the sample.                                   Cut Through Measured in accordance with NEMA                                               Standards Publication Part 3,                                                  paragraph 50.1.1.2.                                                Heat Shock  Tested in accordance with NEMA                                                 Standards Publication, Part 3,                                                 paragraph 4.1.1.                                                   Burn Out    Tested in accordance with NEMA                                                 Standards Publication, Part 3,                                                 paragraph 53.1.1.4. F.O.M. is                                                  Figure of Merit calculated as                                                  described in NEMA Standards                                                    Publication, Part 3, paragraph                                                 53.1.1.3.                                                          A. O. Smith A five-foot sample of wire is                                      Freon Blister                                                                              wound into a coil which produces                                   Test        four to six percent stretch, baked for                                         two hours at 150° C., then cooled                                       to room temperature. The samples                                               are then placed in a freon bomb                                                charged with Freon 22 ® and the                                            pressure in the bomb is brought up                                             to 600 pounds per square inch by                                               heating and held six hours. After                                              the six hour hold, the pressure is                                             immediately released and coils are                                             placed in an oven at 150° C. for                                        four hours. The coils are then                                                 removed from the oven and checked                                              for blistering. One large blister,                                             or two medium, or five small blister                                           constitutes a failure. The wire is                                             then wrapped around a five times                                               mandrel for ten turns and checked                                              for cracks or peeling. If the                                                  coating cracks or peels, it is                                                 a failure. Finally, the wire is                                                made into a twisted pair and                                                   dielectrics are determined in                                                  accordance with NEMA Standards                                                 Publication, Part 3, paragraph                                                 7.1.1.3.                                                           Dielectrics:                                                                   Dry         Determined in accordance with NEMA                                             Standards Publication, Part 3,                                                 paragraph 7.1.1.3.                                                 Wet         After soaking in water for 24 hours,                                           the samples are tested as described                                            above.                                                             Bonding     Determined following the procedure                                             described in NEMA Standards Publication,                                       Part 3, paragraph 57.1.1.2 at the                                              temperature stated under Bonding                                               Temperature.                                                       Dissipation Factor                                                                         Tested in accordance with NEMA                                                 Standards Publication, Part 3,                                                 Paragraph 9.1.1.2.                                                 Heat Aging  Number of hours up to 168 (at 180° C.)                      at 180° C.                                                                          required for a sample to be baked                                              to fail a post winding of around a                                             one times mandrel.                                                 ______________________________________                                    

                                      TABLE 1                                      __________________________________________________________________________                      Example       Example                                                          1             2                                               __________________________________________________________________________     Basecoat         PE     PEI    PE       PEI    PEI    PEI                      Build (mils) bondcoat/base-                                                                     1.0/2.0                                                                               1.0/2.0                                                                               1.0/2.1  0.9/1.9                                                                               1.0/2.0                                                                               1.0/2.0                  coat                                                                           Wire Size (AWG)  18     18     18       24     24     24                       Wire Speed (fpm) 50     50     50       100    120    130                      Appearance, bondcoat/base-                                                                      VSW/VSW                                                                               VSW/VSW                                                                               VSW/VSW+ VSW/VSW                                                                               VSW/VSW                                                                               VSW-/VSW                 coat                                                                           MECHANICAL PROPERTIES                                                          Mandrel, before snap                                                                            1X     1X     1X       1X     1X     1X                       Snap (OK or Fall)                                                                               OK     OK     OK       OK     OK     OK                       Mandrel, after snap                                                                             1X     1X     1X       1X     1X     1X                       Abrasion (gms.)  2000+  2000+  1933     1000+  1000+  1000+                    Windability      25     20                                                     Helical Coil Bonding;                                                          Bond Temp., ° C.                                                                         200    200             200    200    200                      Bond Str., lbs. @ 25°C.                                                                  10.63  16.09           6.6    9.7    9.2                      150° C.   6.40   10.88           4.9    5.2    5.6                      180° C.   3.52   5.87            1.7    0.9    0.8                      200° C.   2.09   2.64            0.4    0.4    0.2                      THERMAL PROPERTIES                                                             Cut Through Temp., °C.                                                                   365    340    355      342    318    316                      Heat Shock, 1X   50     80     70       80     60     70                       (1/2 Hr. at test, 2X                                                                            80     90     80       90     80     80                       temp. 20%, 3X    100    100    100      100    100    100                      pre-stretch), 4X 100    100    100      100    100    100                      Heat Shock Test Temp., °C.                                                               175    200    175      200    200    200                      Burnout (F.O.M.) 5.4    6.67                                                   Heat Aging (hrs.)                                                                               168-OK                                                        ELECTRICAL PROPERTIES                                                          Dielectric Strength, dry                                                                        14.6   15.6                                                   (vpm), wet       11.1   11.1                                                   Dissipation Factor                                                                              11.5   4.92            3.34   3.16   5.45                     CHEMICAL PROPERTIES                                                            A. O. Smith Freon Test;                                                        appearance/flexibility                                                                          Fail   OK/OK                                                  dielectric after test (vpm)                                                    __________________________________________________________________________                      Example                       Example                                                                               Example                                   2                             3      4                        __________________________________________________________________________     Basecoat         PAI/PE PAI    None     None   PEI    PEI                      Build (mils) bondcoat/base-                                                                     1.1/0.7/                                                                              1.0/2.0                1.0/2.0                                                                               1.0/2.0                  coat             2.3                                                           Wire Size (AWG)  18     18     18       18     18     18                       Wire Speed (fpm) 50     50     40       50     50     50                       Appearance, basecoat/base-                                                                      VSW/VSW/                                                                              VSW/VSW                VSW/VSW                                                                               VSW/VSW                  coat             VSW                                                           MECHANICAL PROPERTIES                                                          Mandrel, before snap                                                                            1X     1X     1X       1X     1X     1X                       Snap (OK or Fall)                                                                               OK     OK     OK       OK     OK     OK                       Mandrel, after snap                                                                             1X     1X     1X       1X     1X     1X                       Abrasion (gms.)  2000+  1816   2000+    2000+  1883   1866                     Windability      17     14                                                     Helical Coil Bonding;                                                          Bond Temp., °C.                                                                          200    200    200      200    200    200                      Bond Str., lbs. @  25° C.                                                                19.80  18.65  --       --     21.7   0.4                      150° C.   --     --     --       --     10.9   0.0                      180° C.   4.3    3.43   7.4      3.68   6.2    0.0                      200° C.   --     --     --       --     3.2    0.0                      THERMAL PROPERTIES                                                             Cut Through Temp., °C.                                                                   385    325    280      260                                    Heat Shock, 1X   80     70     80       80                                     (1/2 Hr. at test, 2X                                                                            90     90     90       90                                     temp. 20%, 3X    100    100    100      100                                    pre-stretch), 4X 100    100    100      100                                    Heat Shock Test Temp., °C.                                                               260    260    260      260                                    Burnout (F.O.M.)        8.51   2.46     1.13                                   Heat Aging (hrs.)                                                              ELECTRICAL PROPERTIES                                                          Dielectric Strength, dry                                                                        15.9   11.5                                                   (vpm), wet       14.5   11.2                                                   Dissipation Factor                                                                              28.72  22.26  453.0    1874.0                                 CHEMICAL PROPERTIES                                                            A. O. Smith Freon Test;                                                        appearance/flexibility                                                         dielectric after test (vpm)                                                    __________________________________________________________________________                      Example Example Example Example  Example                                                                             Example                                  5       6       7       8        9    10                      __________________________________________________________________________     Basecoat         PEI     PEI     PEI     PEI      PEI  PEI                     Build (mils) bondcoat/base-                                                                     1.0./2.0                                                                               1.0/2.0 1.0/2.0 1.0/2.1  1.0/2.0                                                                             1.0/2.0                 coat                                                                           Wire Size (AWG)  18      18      18      18       18   18                      Wire Speed (fpm) 50      50      50      50       50   50                      Appearance, bondcoat/base-                                                                      VSW/VSW VSW/VSW VSW/VSW VSW-/VSW Wavy/                                                                               VSW/VSW+                coat                                              VSW                          MECHANICAL PROPERTIES                                                          Mandrel, before snap                                                                            1X      1X      1X      1X            1X                      Snap (OK or Fail)                                                                               OK      OK      OK      OK       Fail OK                      Mandrel, after snap                                                                             1X      1X      1X      1X       --   1X                      Abrasion (gms.)  1800    1950    2000+   1933     --   1808                    Windability                                                                    Helical Coil Bonding;                                                          Bond Temp., °C.                                                                          200     200     200     200      200  200                     Bond Str., lbs. @ 25° C.                                                                 1.8     2.9     16.2    12.5     --   --                      150° C.   1.0     2.0     8.0     5.2      --   --                      180° C.   0.0     1.4     4.7     1.5      0.4  2.8                     200° C.   0.0     1.4     2.2     1.1      --   --                      THERMAL PROPERTIES                                                             Cut Through Temp., °C.                                                  Heat Shock, 1X                                                                 (1/2 Hr. at test, 2X                                                           temp. 20%, 3X                                                                  pre-stretch), 4X                                                               Heat Shock Test Temp., °C.                                              Burnout (F.O.M.)                                                               Heat Aging (hrs.)                                                              ELECTRICAL PROPERTIES                                                          Dielectric Strength, dry                                                       (vpm), wet                                                                     Dissipation Factor                                                             CHEMICAL PROPERTIES                                                            A. O. Smith Freon Test;                                                        appearance/flexibility                                                         dielectric after test (vpm)                                                    __________________________________________________________________________                                           Compara-          Compara-                                Example Example                                                                              Example                                                                               tive              tive                                    11      12    13     Example 1         Example                __________________________________________________________________________                                                             2                      Basecoat         PEI     PEI   PEI    PE       PEI      PEI                    Build (mils) bondcoat/base-                                                                     1.0/2.1 1.0/2.1                                                                              1.0/2.1                                                                               1.0/2.0  1.0/2.0  1.0/2.0                coat                                                                           Wire Size (AWG)  18      18    18     18       18       24                     Wire Speed (fpm) 50      50    50     50       50       90                     Appearance, bondcoat/base-                                                                      VSW-/   SW/VSW                                                                               Hvy    VSW-/VSW VSW-/VSW SW/VSW                 coat             VSW           Grain/VSW                                       MECHANICAL PROPERTIES                                                          Mandrel, before snap                                                                            1X      1X    1X     1X       1X       1X                     Snap (OK or Fail)                                                                               OK      OK    OK     OK       OK       OK                     Mandrel, after snap                                                                             1X      1X    1X     1X       1X       1X                     Abrasion (gms.)  1708    1950  2000+  2000+    1916     1000+                  Windability                                                                    Helical Coil Bonding                                                           Bond Temp., °C.                                                                          200     200   200    200      200      200                    Bond Str., lbs. @ 25° C.                                                                 --      --    --     0.0      0.0      4.7                    150° C.   --      --    --     --       --       0.8                    180° C.   1.35    6.3   5.5    0.0      0.0      0.2                    200° C.   --      --    --     --       --       --                     THERMAL PROPERTIES                                                             Cut Through Temp., °C.         280      285      334                    Heat Shock, 1X                        80       90       50                     (1/2 Hr. at test, 2X                  90       100      70                     temp. 20%, 3X                         100      100      80                     pre-stretch), 4X                      100      100      100                    Heat Shock Test Temp., °C.     175      200      200                    Burnout (F.O.M.)                                                               Heat Aging (hrs.)                                                              ELECTRICAL PROPERTIES                                                          Dielectric Strength, dry                                                       (vpm), wet                                                                     Dissipation Factor                                                             CHEMICAL PROPERTIES                                                            A. O. Smith Freon Test,                                                        appearance/flexibility                                                         dielectric after test (vpm)                                                    __________________________________________________________________________                                                      Compara-                                                                               Compara-                                                               tive    tive                                                                   Example                                                                                Example               __________________________________________________________________________                                                              4                                                     Basecoat         PEI     PE                                                    Build (mils) bondcoat/base-                                                                     1.0/2.1 1.0/2.0                                               coat                                                                           Wire Size (AWG)  18      18                                                    Wire Speed (fpm) 50      50                                                    Appearance, bondcoat/base-                                                                      VSW-/VSW                                                                               SW/VSW                                                coat                                                                           MECHANICAL PROPERTIES                                                          Mandrel, before snap                                                                            1X      1X                                                    Snap (OK or Fail)                                                                               OK      OK                                                    Mandrel, after snap                                                                             1X      1X                                                    Abrasion (gms.)  1750    1608                                                  Windability                                                                    Helical Coil Bonding                                                           Bond Temp., °C.                                                                          200     200                                                   Bond Str., lbs. @ 25° C.                                                                 22.4    21.7                                                  150° C.   11.0                                                          180° C.   2.8                                                           200° C.   0.4                                                           THERMAL PROPERTIES                                                             Cut Through Temp., °C.                                                                   315     395                                                   Heat Shock, 1X   90      20                                                    (1/2 Hr. at test, 2X                                                                            100     30                                                    temp. 20%, 3X    100     40                                                    pre-stretch), 4X 100     40                                                    Heat Shock Test Temp., °C.                                                               175     175                                                   Burnout (F.O.M.) 5.97    5.46                                                  Heat Aging (hrs.)                                                              ELECTRICAL PROPERTIES                                                          Dielectric Strength, dry                                                                        11.1                                                          (vpm), wet                                                                     Dissipation Factor                                                             CHEMICAL PROPERTIES                                                            A. O. Smith Freon Test,                                                        appearance/flexibility -dielectric after                                       test (vpm)                                     __________________________________________________________________________

It is critical to use terephthalic acid in copolyamides of the invention. Thus if in place of terephthalic acid there is used isophthalic acid in whole or in part as taught by Onder U.S. Pat. No. 4,072,665, the bond strength is reduced.

Thus there were prepared copolyamides similar to Example 1 replacing the terephthalic acid in whole or in part by isophthalic acid.

COMPARATIVE EXAMPLE 5

The procedure was similar to Example 1 but there were used as reactants a 70/30 molar ratio mixture of toluene diisocyanate and methylene diisocyanate and there was used a 65/25/10 molar mixture of dodecanedioic acid, isophthalic acid and terephthalic acid.

COMPARATIVE EXAMPLE 6

The procedure was the same as in Comparative Example 5 except the dibasic acids employed was 65/35 molar mixture of dodecanedioic acid and isophthalic acid.

Examples 1 and 3 which are within the present invention both employ a 65/35 molar mixture of dodecanedioic acid and terephthalic acid. The bond strength of Comparative Example 5, Comparative Example 6, Example 1, and Example 3 were tested by coating their resultant enamel solutions on top of ISOMID-coated wire at 50 ft./min., followed by bonding at 200° C. for 20 minutes under 1-kg load. The results were as set forth in Table 2:

                  TABLE 2                                                          ______________________________________                                         Test              Bond Strength,                                               Specimen          Lbs. at 180° C.                                       ______________________________________                                         Comparative Example 5                                                                            4.75                                                         Comparative Example 6                                                                            3.2                                                          Example 1         5.9                                                          Example 3         6.2                                                          ______________________________________                                    

It can be seen from Table 2 that the greater the replacement of terephthalic acid by isophthalic acid the greater the reduction in bond strength. 

What is claimed is:
 1. A self-bondable laminate of a copolyamide having the recurring unit ##STR4## where AL is the divalent hydrocarbon residue of an unsubstituted aliphatic dicarboxylic acid having at least 6 carbon atoms, R is tolylene, phenylene, ##STR5## where F is O, CH₂, or SO₂ or is a cycloaliphatic hydrocarbon, Ar is p-phenylene, y is 35 to 80% of the recurring units and z is 65 to 20% of the recurring units coated onto a film of a polymer selected from the group consisting of a different polyamide, polyamide-imide, polyimide, poly-parabanic acid, polyester and perfluoroolefin polymer.
 2. A self-bondable laminate according to claim 1 wherein R is tolylene, phenylene, ##STR6## where F is O, Ch₂, or SO₂. 